WO2017064835A1 - Target information detection system and target information detection method - Google Patents

Abstract

In order to make it possible to separately detect a plurality of targets having the same speed using a narrow-band RF signal and BB signal by an inexpensive and easily designed means, the target information detection system according to the present invention includes a measurement-side speed detection device for detecting the speed of a measurement-side moving body as a moving body speed, and a target-side speed detection device for detecting the speed of a target as a target speed, and when it is determined from a Doppler frequency that the relative speed of the measurement-side moving body and the target is equal to or less than a mode switching speed set in advance, a target information detection device switches a target information detection mode from a Doppler mode to a communication mode, acquires a moving-body speed via the measurement-side speed detection device and acquires a target speed via the target-side speed detection device, and calculates target information using the moving-body speed and the target speed.

Description

Target information detection system and target information detection method

The present invention relates to a target information detection system and a target information detection method for measuring target information such as a distance to a target and a relative speed.

The on-vehicle radar emits radio waves toward targets such as other vehicles and obstacles, and receives the reflected waves reflected by this target. Then, the presence of the target, the distance to the target (target distance), and the relative speed of the target are measured by analyzing the received signal based on the received wave (reflected wave). Hereinafter, the presence of the target, the target distance, and the relative speed of the target are collectively referred to as target information.

Such an on-vehicle radar is used as a system for improving the movement safety of an automobile such as a collision mitigation (braking) system or a preceding vehicle following system. At this time, it is important to improve the detection resolution of the target in order to improve reliability and safety of movement.

Generally, the detection resolution in the distance direction is improved by widening the RF (Radio Frequency) signal and the baseband signal (BB signal) used as the base of the radiated radio wave. However, it is desirable to reduce the bandwidth of the RF signal and the baseband signal (BB signal) while improving the detection resolution. This is because by narrowing the signal bandwidth, circuit design with the required detection resolution can be facilitated, and the system cost can be reduced. Furthermore, if a desired detection resolution can be obtained with a narrow RF signal bandwidth, the number of channels that can be used increases, so there is an advantage that radio wave interference between in-vehicle radars is suppressed.

As such an on-vehicle radar, FMCW (Frequency Modulated Continuous Wave) radar, pulse radar, and pulse compression radar are known. Also, multi-frequency CW radar using continuous wave (CW: Continuous Wave) that switches the frequency in time, multi-frequency ICW (Interrupted Continuous Wave) radar that combines multi-frequency CW radar system and pulse radar system (see Non-Patent Document 1) ) Has been proposed. Furthermore, a multi-frequency CPC (Complementary Phase Code) radar system (see Non-Patent Document 2) that combines a multi-frequency CW radar system and a pulse compression radar system has been proposed.

Here, the required bandwidths of the RF signal and the BB signal in various in-vehicle radars are examined. 7, using the RF signal of frequency f _c is 60.5 [GHz], is a diagram summarizing the bandwidth of the RF signal and BB signal required in detecting the target at a predetermined detection resolution. The target is located in front of the on-vehicle radar, the target distance R is R = 50 [m], and the speed V is V = 30 [km / h]. The distance resolution ΔR is set to ΔR = 0.3 [m], and the speed resolution ΔV is set to ΔV = 0.3 [km / s].

In FIG. 7, the signal bandwidth in each of the FM-CW method, the two-frequency CW method, the pulse method, and the pulse compression method was calculated from the formula shown in the lower column of each method (see Non-Patent Document 3). In addition, the value of the signal bandwidth in the multi-frequency CPC method refers to the actual measurement value in Non-Patent Document 2. In the two-frequency CW method, the number of frequencies used in the multi-frequency CW method is two.

7 that the two-frequency CW method that can suppress both the bandwidth of the RF signal and the BB signal is effective to achieve the desired distance resolution ΔR.

Note that both the FM-CW method and the pulse / pulse compression method require a wide RF signal bandwidth given by c / (2ΔR). Here, c is the speed of light, and ΔR is the distance resolution. In addition, the multi-frequency CPC method is a method in which the multi-frequency CW method and the pulse compression method are combined. However, the RF signal bandwidth of the same level as the pulse compression used for the combination is still required.

The 2-frequency CW system (or multi-frequency CW system) has an advantage that both the bandwidth of the RF signal and the BB signal can be suppressed. However, when there are a plurality of targets having the same speed as the in-vehicle radar, there is a problem that each target cannot be individually recognized (target information corresponding to each target cannot be acquired).

The problem in the two-frequency CW method will be described with reference to the block diagram of the on-vehicle radar in the two-frequency CW method shown in FIG. 8 (see Non-Patent Document 3).

First, the calculation principle of the target distance will be described. FIG. 8 is a block diagram of a two-frequency CW system on-vehicle radar. This on-vehicle radar includes an antenna 101, a circulator 102, a mixer 103, a low-pass filter (LPF) 104, an oscillator 105, an analog-digital (A / D) converter 106, a Fourier transform unit 107, a calculator 109, and a controller 110. It consists of Incidentally, the Fourier transform unit 107 is provided with two of Fourier transformer 108 ₁ and Fourier transformer 108 _2.

Then, as shown in FIG. 9, the oscillator 105 switches the RF signals (transmission signals) of the _two frequencies f ₁ and f ₂ in accordance with instructions from the controller 110 and outputs them to the circulator 102 and the mixer 103. In FIG. 9, Tc is a period.

The RF signal output from the oscillator 105 to the circulator 102 is output as a transmission wave Wt via the antenna 101. This transmission wave Wt is reflected by the target T and received by the antenna 101 as a reception wave Wr.

The frequency of the reception wave Wr is subjected to the Doppler effect by the target T having the relative velocity V, and is shifted by the Doppler frequency f _d (= 2V / λ, λ is the wavelength of the transmission wave Wt) with respect to the frequency of the transmission wave Wt (Doppler). shift.

The received wave Wr received by the antenna 101 is input to the mixer 103 via the circulator 102. The mixer 103 mixes the transmission signals of the frequencies f ₁ and f ₂ and the reception signals of the reception frequencies f ₁ + f _d and f ₂ + f _d from the oscillator 105, and outputs them to the A / D converter 106 via the BPF 104. To do. A signal input to the A / D converter 106 is referred to as a beat signal. The frequency of the beat signal is, the Doppler frequency f _d.

If the beat signal when the frequency of the RF signal output from the oscillator 105 is f ₁ and f ₂ is S _f1 (t) and S _f2 (t) and the indefinite constant of the in-vehicle radar is φ ₀ , the beat signal S _f1 (t) and S _f2 (t) are
S _f1 (t) ∝cos [2πf _d t−4πf ₁ R / c + φ ₀ ] (1)
S _f2 (t) ∝cos [2πf _d t−4πf ₂ R / c + φ ₀ ] (2)
Are given by Equations 1 and 2.

The beat signal is converted into a digital signal by the A / D converter 106 and input to the Fourier transform unit 107, and the spectrum phase is obtained by the Fourier transform unit 107.

When the frequency of the transmission wave Wt is f ₁ , the Fourier transformer 108 ₁ calculates the spectrum phase φ ₁ (= φ ₀ −4πf ₁ R / c) of the reception wave Wr. Further, when the frequency of the transmission wave Wt is f ₂ , the spectrum phase φ ₂ (= φ ₀ −4πf ₂ R / c) of the reception wave Wr is calculated by the Fourier transformer 108 ₂ .

The Fourier transformers 108 ₁ and 108 ₂ used for the calculation of the spectrum phase are selected in synchronization with the frequency switching timing signal of the RF signal (transmitted wave Wt) output from the controller 110 to the oscillator 105, and the Fourier transform unit. This is performed based on the instruction output to 107.

The calculator 19 determines that the difference Δφ between the spectrum phases φ ₁ and φ ₂ of the beat signals S _f1 (t) and S _f2 (t) is Δφ = φ ₁ −φ _2.
Therefore, using this, the target distance R is
R = cΔφ / 4π (f ₂ −f ₁ ) (3)
It calculates with the formula 3 of.

Next, based on such a target distance calculation principle, consider a case where _two targets T ₁ and T ₂ are detected simultaneously as shown in FIG. At this time, the relative speeds of the _two targets T ₁ and T ₂ are set to V ₁ and V ₂ , respectively.

The beat signal output from the BPF 104 is a superposition of the beat signal S _{1 from the} target T ₁ included in the received wave Wr and the beat signal S _{2 from the} target T ₂ (S = S ₁ + S ₂ ). The frequencies of the beat signals S ₁ and S ₂ are Doppler frequencies f _d1 = 2V ₁ / λ and f _d2 = 2V ₂ / λ, respectively. That is, when the targets T ₁ and T ₂ are detected at the same time, the spectrum of the beat signal is in a state in which two spectra consisting of the beat signals S ₁ and S ₂ are standing as shown in FIG.

At this time, when the speeds V ₁ and V ₂ are different between the _two targets T ₁ and T ₂ (V ₁ ≠ V ₂ ), the Doppler frequencies f _d1 = 2V ₁ / λ and f _d2 = of the beat signals S ₁ and S ₂ 2V ₂ / λ is also a different value (f _d1 ≠ f _d2 ). Therefore, as shown in FIG. 11, the spectrum of the beat signals S ₁ and S ₂ is observed as a spectrum having different frequencies, so that the spectrum phases of the beat signals S ₁ and S ₂ can be obtained separately. Therefore, the target distances of the targets T ₁ and T ₂ can be calculated individually from the detected spectral phase and Equation 3.

On the other hand, when the speeds V ₁ and V _{2 of} the targets T ₁ and T ₂ are the same (V ₁ = V ₂ ), the frequencies f _d1 = 2V ₁ / λ and f _d2 = 2V ₂ / λ of the beat signals S ₁ and S ₂ Also have the same value (f _d1 = f _d2 ). Therefore, as shown in FIG. 12, the spectrum phases of the beat signals S ₁ and S ₂ have the same frequency, and the beat signals S ₁ and S ₂ cannot be detected separately. Therefore, there arises a problem that the target distances of the targets T ₁ and T ₂ cannot be calculated individually.

As a method for solving such problems of the two-frequency CW method, Patent Document 1 proposes a method (equivalent to the multi-frequency CPC method) in which a multi-frequency CW method and a pulse method are combined.

This proposal switches from the 2-frequency CW method to another radar method in a situation where the 2-frequency CW method cannot be used (when the relative speed of the target is “0” or there are a plurality of targets having the same speed).

Here, unlike the two-frequency CW method, the other radar methods can detect the target even in a situation where the two-frequency CW method cannot be used (when the relative speed of the target is “0” or there are a plurality of targets having the same speed). Make it possible. For example, the FMCW system in Patent Documents 1 and 2, the FMCW system in Patent Documents 3 and 4 or the frequency pulse CW system, and the 2-frequency Ramp modulation system in Patent Documents 5 and 6 can be exemplified.

JP 2000-292530 A JP 2002-71793 A JP 2004-69693 A JP 2006-317456 A JP 2006-258709 A JP 2009-36514 A JP 2009-244136 A Japanese Patent Laid-Open No. 2003-167048 JP 2009-44A1 Japanese Patent Laid-Open No. 11-198678 JP 2006-163615 A JP 2013-250147 A

However, in each method described above, when the relative speed between the in-vehicle radar and the target is “0” or the like, when a method other than the two-frequency CW method is used, the RF signal or the BB signal has a wide band. There are problems that design becomes difficult and system cost increases. Furthermore, there is a risk that radio frequency interference may occur while the spectral efficiency decreases due to the broadening of the RF signal.

Further, in order to enable detection of a target even when there are a plurality of targets having the same speed, an RF signal or a BB signal is generated even in a method using a time waveform combining a multi-frequency CW method and a pulse method in Patent Document 7 for a radar. There is a problem of wide bandwidth.

Also, as a method of detecting a target having a relative speed of “0” using the two-frequency CW method, a received wave and a high-speed sawtooth wave are mixed using a normal two-frequency CW waveform in the transmission wave of Patent Document 8. In this case, since a plurality of targets having the same speed are detected separately, the bandwidth of the RF signal (transmission wave) may be narrow, but the bandwidth of the BB signal becomes wide due to the influence of the sawtooth wave. For this reason, there are problems that circuit design becomes difficult and system cost increases.

As a method for solving the first and second problems of the two-frequency CW method, as disclosed in Patent Document 9, the transmission frequency of the transmission radio wave is set at a timing synchronized with the sample frequency of A / D conversion. A method of switching has been proposed. However, this method also has a problem that the RF signal has a wide band. In the example of Patent Document 9, the bandwidth of the RF signal is 1 GHz.

Furthermore, as a method for solving the problems of the two-frequency CW system, as disclosed in Patent Document 10, when the relative speed between the in-vehicle radar and the target approaches “0”, the in-vehicle is changed so that the relative speed is changed. In the method of controlling the speed of a vehicle equipped with a radar (throttle / brake), there is a problem that the speed of the vehicle becomes unstable.

Accordingly, a main object of the present invention is to provide a target information detection apparatus and a target information detection method that can be easily designed and can separately detect a plurality of targets having the same speed by using a narrow band RF signal and a BB signal at low cost. Is to provide.

In order to solve the above problems, target information is obtained by irradiating a plurality of targets with a transmission wave having a predetermined frequency from a measurement-side moving body, and obtaining the distance between the measurement-side moving body and the target as target information from the Doppler frequency included in the reflected wave. The invention according to the detection system includes a target information detection device that calculates target information based on a Doppler frequency, a measurement-side speed detection device that detects the speed of a measurement-side moving body as a moving-body speed, a target information detection device, and a measurement-side speed. A measurement-side communication device that includes at least a measurement-side communication device that communicates with the detection device, a measurement-side unit mounted on the measurement-side moving body, a target-side speed detection device that detects a target velocity as a target velocity, and a target-side velocity detection device And a target-side communication device that communicates with the measurement-side communication device. A target unit mounted on the target, and the target information detection device determines from the Doppler frequency that the relative speed between the measurement-side moving body and the target is equal to or lower than a preset mode switching speed. Switches the target information detection mode from the Doppler mode to the communication mode, acquires the moving body speed via the measurement side communication apparatus, and acquires the target speed via the measurement side communication apparatus and the target side speed detection apparatus. The target information is calculated using the moving body speed and the target speed. Further, a plurality of targets are irradiated with a transmission wave having a predetermined frequency from the measuring-side moving body, and the Doppler frequency included in the reflected wave is calculated. Information detection that determines the distance between the measurement-side moving object and the target as target information According to the present invention, the target information is calculated based on the Doppler frequency by the target information detection device, the velocity of the measurement-side moving body is calculated as the moving-body velocity by the measurement-side velocity detection device, and the target-information detection device is calculated by the measurement-side communication device And the target side speed detection device detects the target speed as the target speed, the target side communication device communicates with the target side speed detection device and the measurement side communication device, and measures from the Doppler frequency. When the relative speed between the side moving body and the target is less than or equal to the preset mode switching speed, the target information detection mode is switched from the Doppler mode to the communication mode, and the moving body speed is acquired via the measurement side communication device. And the measurement side communication device and the target side speed detection device To obtain the target speed through, and calculates the target information using the mobile speed and the target speed, characterized in that.

According to the present invention, it is possible to provide a target information detection apparatus and a target information detection method that are easy to design and can separately detect a plurality of targets having the same speed by using a narrow band RF signal and a BB signal. .

It is explanatory drawing of the target information detection system concerning 1st Embodiment. It is a flowchart which shows a target information detection procedure. It is a figure explaining target information detection by the target information detection system concerning a 2nd embodiment. It is a block diagram of a target information detection apparatus. It is the figure which illustrated each frequency in an oscillator. It is explanatory drawing of the target information detection system concerning 3rd Embodiment. It is the figure which put together the bandwidth of RF signal and BB signal which are applied when explanation of a related art is necessary for detecting a target by predetermined detection resolution. It is a block diagram of the vehicle-mounted radar in a 2 frequency CW system. It is the figure which illustrated RF signal (transmission signal) of two frequencies. It is a block diagram of the vehicle-mounted radar at the time of detecting two targets simultaneously. It is the figure which illustrated the beat signal from which frequency differs. It is the figure which illustrated the beat signal with the same frequency.

<First Embodiment>
An embodiment of the present invention will be described. FIG. 1 is an explanatory diagram of a target information detection system 2 according to the present embodiment. The target information detection system 2 includes a measurement side unit 3 and a target side unit 4.

In FIG. 1, a vehicle (moving body) A and a vehicle (target) B are illustrated, the measurement side unit 3 is mounted on the vehicle A, and the target side unit 4 is mounted on the vehicle B. At this time, FIG. 1A shows the case where the speed of the vehicle A> the vehicle B, FIG. 1B shows the case where the speed of the vehicle A≈the vehicle B, and FIG. 1C shows the case where the speed of the vehicle A <the vehicle B. Yes.

Then, the inter-vehicle distance (target information) between the vehicle A and the vehicle B is acquired by the measurement side unit 3 mounted on the vehicle A. The target information may include information on the relative speed between the vehicle A and the vehicle B, the presence of the vehicle B, and the like. Vehicle A and vehicle B are examples, and are not limited to vehicles. For example, it may be a transport carrier in a factory, and the vehicle B may be a stationary object.

The measurement side unit 3 includes a measurement side speed detection device 3A, a measurement side communication device 3B, and a target information detection device 3C. The measurement-side speed detection device 3A detects the speed of the vehicle A (moving body speed). The measurement-side communication device 3B communicates with the target information detection device 3C and the measurement-side speed detection device 3A, and also communicates with the target-side communication device 4B. The target information detection device 3 </ b> C detects target information of the vehicle B based on a Doppler frequency or the like based on the relative speed between the vehicle A and the vehicle B.

The target side unit 4 includes a target side speed detection device 4A and a target side communication device 4B. The target-side speed detection device 4A detects the target speed (target speed). The target side communication device 4B communicates with the target side speed detection device 4A and the measurement side communication device 3B.

The measurement-side speed detection device 3A and the target-side speed detection device 4A may be a speed detection device such as a speed meter attached to each vehicle A or vehicle B (may be used in combination).

When the target information detection device 3C determines from the Doppler frequency that the relative speed between the vehicle A and the vehicle B is equal to or lower than the predetermined speed, the target information detection device 3C acquires the moving body speed via the measurement-side communication device 3B. The target speed is acquired via the measurement side communication device 3B and the target side speed detection device 4A. Thereafter, the target information detection device 3C calculates target information using the moving body speed and the target speed. Note that the target information detection device 3C is desirably a two-frequency CW method (or a multi-frequency CW method).

Hereinafter, it is assumed that the speeds of the vehicles A and B are V _A and V _B , the vehicle B moves in front of the vehicle A, and the vehicles A and B are moving in the same direction. However, the present embodiment is not limited to such conditions. That is, the vehicle B may be moving in the direction opposite to the moving direction of the vehicle A. Therefore, the irradiation direction of the transmission wave Wt is not limited to the moving direction of the vehicle A. Assuming such various cases, the irradiation direction of the transmission wave Wt may be radiated forward, backward, left and right at predetermined time intervals.

The target information detection procedure will be described with reference to the flowchart shown in FIG.

Steps S1, S2: When the process is started, the target information detection mode is set to the Doppler mode. The target information detection mode includes a Doppler mode in which target information is acquired from the Doppler frequency and a communication mode in which target information is acquired from an actual measurement value of relative speed.

In this state, the target information detection device 3C transmits N transmission signals having different frequencies and receives a reflected wave from the target. Then, the Doppler frequency is calculated from the difference between the transmission signal and the reception signal.

Step S3: The Doppler frequency is proportional to the relative speed between the vehicle A and the target T. Therefore, it is determined whether or not the calculated absolute value of the relative speed is equal to or less than a preset mode switching speed. The target distance is calculated by integrating the relative speeds of the vehicles A and B as will be described later. Therefore, when speed V _A ≈ speed V _B (that is, absolute value of relative speed ≦ mode switching speed), measurement errors of speed V _A and speed V _B are accumulated and increased, and the detection accuracy of the target distance is increased. It will decrease. The mode switching speed is a value set according to the detection accuracy of the allowable target distance.

The relative speeds of the vehicles A and B are (1) when the speed V _A > the speed V _B (corresponding to FIG. 1 (a)), (2) when the speed V _A ≈the speed V _B (FIG. 1 (b) ), And (3) the case where the speed V _A <the speed V _B (corresponding to FIG. 1C). When (1) Speed V _A > Speed V _B and (3) Speed V _A <Speed V _B , the absolute value of the relative speed> Mode switching speed, and (2) Speed V _A ≈ Speed for V _B, an absolute value ≦ mode switching speed of the relative velocity.

(1) When speed V _A > speed V _B , and (3) When speed V _A <speed V _B , the absolute value of the relative speed> mode switching speed, so the target information detection device 3C switches to the Doppler mode. Then, target information is calculated using the Doppler frequency (proceeding to step S4). On the other hand, in the case of (2) speed V _A ≈ speed V _B , the absolute value of the relative speed ≤ the mode switching speed, so switch to the communication mode (proceed to step S5), and integrate the measured relative speed to obtain the target distance. calculate.

Step S4: (in the case of absolute value of relative speed> mode switching speed: Doppler mode)
In this case, the distance (target distance) between the vehicle A and the vehicle B decreases with the passage of time (the vehicle A and the vehicle B approach each other), or the target distance increases with the passage of time ( Vehicle A and vehicle B are separated). That is, the relationship of absolute value of relative speed> mode switching speed is satisfied.

The frequency of the reception wave Wr is Doppler modulated according to the relative speed between the vehicle A and the vehicle B with respect to the transmission wave Wt, and the frequency of the reception wave Wr is shifted by the Doppler frequency f _{d with} respect to the frequency of the transmission wave Wt. Frequency. Therefore, the target information detection device 3C calculates the Doppler frequency based on the transmission wave Wt and the reception wave Wr, and acquires target information such as the relative position, target distance, and relative speed of the vehicle B.

Note that when mode switching is performed, it is preferable to reset the target information regarding the vehicle B acquired in the previous mode in order to improve the accuracy of the target information in each mode. This reset process means resetting the initial value.

Steps S5 to S7: (In the case of absolute value of relative speed ≦ mode switching speed: communication mode)
On the other hand, when speed V _A ≈speed V _B , as shown in FIG. 1B, the relationship of absolute value of relative speed ≦ mode switching speed is satisfied, so that there is almost no change in the target distance with time. In such a case, in the two-frequency CW method (or the multi-frequency CW method), the Doppler frequency f _d becomes f _d ≈0, so that it is difficult to acquire the target information of the vehicle B with high accuracy.

Therefore, when the target information detection device 3C determines that the Doppler frequency f _d ≈0, the target information detection device 3C outputs a speed request command to the measurement-side communication device 3B. When receiving the speed request command, the measurement side communication device 3B requests the current speed of the own device (vehicle A) from the measurement side speed detection device 3A. Thereby, the speed V _A of the vehicle A is sent from the measurement side speed detection device 3A to the target information detection device 3C via the measurement side communication device 3B.

Further, when receiving the speed request command, the measurement side communication device 3B transmits the speed request command to the target side communication device 4B. When the target side communication device 4B receives this speed request command, the target side communication device 4B acquires the current speed of the target (vehicle B) from the target side speed detection device 4A, and sends it to the target information detection device 3C via the target side communication device 4B. Send.

By these processes, the target information detection apparatus 3C acquires the speed _{V B} of the speeds _{V A} and the vehicle B of the vehicle A, the relative speed [Delta] V a _{ΔV = V B -V A ... (} 4)
This is calculated according to Equation 4 below.

Then, the target information detection device 3C uses this relative speed to change the target distance R to R = R ₀ + ∫ΔV · dt (5)
This is calculated according to Equation 5 below. Here, R ₀ is a target distance between the vehicle A and the vehicle B at the time of mode switching.

As described above, when the target information is acquired using the two-frequency CW method (or the multi-frequency CW method) and the Doppler frequency cannot be measured with high accuracy (the absolute value of the relative speed ≦ the mode switching speed) However, by using the measurement side speed detection device, the measurement side communication device, the target side speed detection device, and the target side communication device, the presence of the vehicle B can be detected with high accuracy and the target information can be acquired. Will be able to.

Second Embodiment
Next, a second embodiment of the present invention will be described. In addition, about the same structure as 1st Embodiment, description is abbreviate | omitted suitably using the same code | symbol.

In the first embodiment, by separately using communication means and speed detection means, target information of the target can be acquired even when the target is moving at the same speed as the own device. However, when there are a plurality of targets, each target cannot be identified and the target information cannot be acquired. Therefore, in this embodiment, target information of each target can be acquired even in such a case.

FIG. 3 is a diagram for explaining target information detection by the target information detection system 2 in such a system. The vehicle (mobile unit) A moving at velocity V _A, and detects the vehicle target information (second type target) C moving vehicle moving at a speed V _B (Type 1 target) B, at a velocity V _C Yes.

The vehicle A is equipped with a measurement-side speed detection device 3A, a measurement-side communication device 3B, and a target information detection device 3C. In addition, the vehicle B is equipped with a target-side speed detection device 4A and a target-side communication device 4B. However, the vehicle C does not include such speed detection means and communication means. Further, the front-rear relationship between the vehicle B and the vehicle C as viewed from the vehicle A does not matter.

FIG. 4 is a block diagram of the target information detection apparatus 3C. The target information detection apparatus 3C includes at least an antenna 11, a circulator 12, a mixer unit 13, an oscillator 15, a Fourier transform unit 17, a calculator 19, and a controller 20. The mixer unit 13 includes a mixer 13a, a band pass filter (BPF) 13b, and an analog-digital (A / D) converter 13c. The Fourier transform unit 17 includes N Fourier transformers 18 ₁ ... 18 _N.

The target T is composed of M targets T ₁ ... T _M , and each target T is moving at the same speed. Then, the target information detection device 3C identifies a plurality of targets T and acquires target information of each target. In FIG. 4, the target T is also illustrated, but it is added that the target T does not constitute the target information detection device 3 </ b> C.

Thus, in order to acquire target information of a plurality of targets T, as described above, the Fourier transform unit 17 is configured by _N Fourier transformers 18 ₁ ... 18 _N. In the following, each Fourier transformer 18 ₁ ... 18 _N is different only in the frequency of the signal to be processed, and therefore a common description may be described as a Fourier transformer 18 or a Fourier transformer 18 _i .

The oscillator 15 outputs RF signals (transmission signals) G3 having _N frequencies f ₁ ... F _N. FIG. 5 is a diagram illustrating frequencies f ₁ ... F _N in the oscillator 15. Again, there may be described a frequency _f 1 ... _{f N} and frequency f or frequency _{f i.}

The number M of targets T, the number N of Fourier transformers 18, and the number N of frequencies f are positive integers and are required to satisfy the relationship of N ≧ M + 1 as will be described later.

The controller 20 outputs a frequency switching command G1 to the oscillator 15 and outputs a Fourier transformer switching command G2 to the Fourier transform unit 17 in synchronization with the frequency switching command G1. Thus, the oscillator 15 outputs a transmission signal G3 of a frequency f _i that is specified by the frequency switching command G1 to the circulator 12 and the mixer unit 13. Further, the Fourier transform unit 17, selects the Fourier transformer 18 _i corresponding to the specified frequency _{f i} in the Fourier transformer switching command G2, the selected Fourier transformer 18 _i is FFT was (Fast Fourier Transform) conversion Process.

Such target information detection apparatus 3C operates as follows. First, the transmission signal G3 output from the oscillator 15 to the circulator 12 is irradiated from the antenna 11 toward the target T as a transmission wave Wt. The irradiated transmission wave Wt is reflected by the target T and received by the antenna 11 as a reception wave Wr.

When the transmission wave Wt is reflected by the target T, it is modulated by the Doppler effect. That is, the frequency of the reception wave Wr becomes a frequency that is Doppler shifted by the Doppler frequency f _di (= 2V _i / λ) with respect to the frequency of the transmission wave Wt by the target T _i of the speed V _i .

The received wave Wr is received by the antenna 11 and input to the mixer unit 13 via the circulator 12 as a received signal. The mixer 13a mixes the reception signal and the transmission signal, and outputs the mixed signal as a beat signal to the A / D converter 13c via the BPF 13b.

Beat signal _S M (t, _{f i)} in the case of the frequency of the transmitted signal G3 is _{f i} is,
S _M (t, f _i ) = ΣB _j (6)
Given in. Note that Σ means the sum of 1 ... M for j. Where B _j is
B _j = A _j · sin [2πf _dj t + φ ₀ -4πf _i R _j / c]
It is. B _j is the beat signal of the received signal by the reflected received wave Wr at each target T _j. That is, the beat signal S _M (t, f _i ) in Expression 6 is the sum of the beat signals based on the received signals from the respective targets T. R _j is the target distance of each target T _j , A _j is the amplitude of the beat signal obtained from the received signal from the target T _j , and φ ₀ is an indefinite constant.

The beat signal is converted into a digital signal by the A / D converter 13c, and an FFT conversion process is performed by the Fourier transform unit 17 to calculate a spectrum phase. At this time, Fourier controller 20, when instructed to output the transmission signal G3 of the frequency f _i with the frequency switching command G1 relative to oscillator 15, corresponding to the frequency f _i for the Fourier transform unit 17 The converter 18 _i is instructed to perform the FFT conversion process.

The computing unit 19 calculates the target distance R _i using the spectral phase calculated by the Fourier transformer 18 _i .

Next, the procedure for calculating the target distance will be described. For simplicity of explanation, two targets T ₁ and T ₂ having the same speed are considered.

In this case, the Doppler frequencies by the targets T ₁ and T ₂ are f _d1 and f _d2 , and these are f _d1 = f _d2 (≡f _d ). Therefore, the beat signal S _M (t, f _i ) shown in Equation 6 is
S ₂ (t, f _i ) = B ₁ + B ₂ (7)
Is given by Equation 7. Where B ₁ and B ₂ are
B ₁ = A ₁ · sin [2πf _d t + φ ₀ -4πf _i R ₁ / c]
B ₂ = A ₂ · sin [2πf _d t + φ ₀ -4πf _i R ₂ / c]
It is.

When the beat signal S ₂ (t) of Equation 7 is transformed,
S ₂ (t, f _i ) = A ₁₂ (f _i ) · sin [2πf _d t + Φ ₁₂ (f _i )] (8)
It becomes.

Where {A ₁₂ (f _i )} ² and Φ ₁₂ (f _i ) are
{A ₁₂ (f _i )} ² = A ₁ ² + A ₂ ² + 2A ₁ A ₂ cos [K · f _i (R ₂ −R ₁ )] (9)
Φ ₁₂ (f _i ) ≡φ ₀ −K · f _i · R ₁ + tan ⁻¹ [X (A ₁ , A ₂ , R ₁ , R ₂ , f _i )] (10)
It is.

K is a constant,
K≡4π / c (11)
Given in. The function X (A ₁ , A ₂ , R ₁ , R ₂ , f _i ) is
X (A ₁ , A ₂ , R ₁ , R ₂ , f _i ) ≡A ₂ · sin (K · f _i (R ₂ −R ₁ )) / [A ₁ + A ₂ · cos (K · f _i (R ₂ -R ₁ ))] ... (12)
Given in.

If each target T ₁ , T ₂ has the same speed, from Equation 8, the beat signal S ₂ (t, f _i ) will contain only a single Doppler frequency f _d .

The amplitude A ₁₂ (f _i ) and the phase Φ ₁₂ (f _i ) of the beat signal expressed by the equations 8 to 10 are values based on the observation result, and the frequency f _i of the transmission signal G3 output from the oscillator 15 is expressed as follows. When changed, each takes a different value.

For N transmission signals of frequencies f ₁ ... F _N , Expressions 7 and 8 hold N expressions, respectively. Therefore, the total number of expressions is 2N.

The unknowns included in the formula 9 and formula _{10, A 1, A 2, φ} 0, R 1, a total of five _{R 2.} Therefore, if the number N of frequencies is one more than the number M (= 2) of targets (N ≧ M + 1), the number of equations (= 2N ≧ 2 (M + 1) = 6) is larger than the number of unknowns. From the equations obtained, the same number of equations as the number of unknowns is selected and the unknowns can be determined by solving the equations. Incidentally, R ₁ can be obtained according to the procedure of the first embodiment. For this reason, there are a total of four unknowns A ₁ , A ₂ , φ ₀ , and R ₂ .

This makes it possible to solve Equation 9 and Equation 10, and it is possible to identify a plurality of targets moving at the same speed and detect target information of each target.
<Third Embodiment>
A third embodiment of the present invention will be described. In addition, about the same structure as 1st, 2 embodiment, description is abbreviate | omitted suitably using the same code | symbol.

In the present embodiment, there are a plurality of vehicles (first type targets) B including a target side speed detection device 4A and a target side communication device 4B, and vehicles (second type targets) C not including these, and each When the vehicle moves at the same speed, the target information of each target is acquired individually.

FIG. 6 is an explanatory diagram of such a target information detection system 2. In the following description, the first type target vehicle B is described as p units (vehicles B ₁ ... B _p ), and the second type target vehicle C is described as q units (vehicles C ₁ ... C _q ). Therefore, the target number M is M = p + q. FIG. 6 illustrates a case where there are two vehicles B and C (p = q = 2).

If the target is the same speed, the Doppler frequency _{f dj} in beat signal _{S M} of the formula 6 is a value equal all the same frequency _(f dj = f _d).

That is, the beat signal S _M given by the equation 6, since the sum of the beat signal by the M targets having the same frequency f _d,
S _M (t, f _i ) = A _{12... M} (f _i ) · sin [2πf _i t + Φ _{12... M} (f _i )] (13)
Is expressed as shown in Equation 13.

In addition, if the inductively to represent the beat signal S _M of the formula 6,
S _M (t, f _i ) = S _(M−1) (t, f _i ) + A _M · sin [2πf _d t + φ ₀ −4πf _i R _M / c] (14)
S _(M−1) (t, f _i ) = A _{12 (M−1)} (f _i ) · sin [2πf _d t + Φ _{12 (M−1)} (f _i )] (15)
Equations 14 to 15 are obtained as follows.

The amplitude and phase of the beat signal S _M (t, f _i ) when there are M targets, and the beat signal S _(M−1) (t, f _i ) when there are (M−1) targets. The relationship between the amplitude and phase of
{A _{12... M} (f _i )} ² = {A _{12... (M−1)} (f _i )} ² + A _M ² + 2A _{12... (M−1)} (f _i ) · A _M cos [α (Φ _{12 ... (M-1)} (f _i ), R _M , f _i , φ ₀ )] ... (16)
Φ _{12... M} (f _i ) = Φ _{12... (M−1)} (f _i ) + tan ⁻¹ [β (A _{12... (M−1)} (f _i ), A _M , R _M , f _i , φ ₀ )] (17)
Are given by Equation 16 and Equation 17.

here,
α (Φ _{12... (M−1)} (f _i ), R _M , f _i , φ ₀ ) = φ ₀ −4π f _i R _M / c + Φ _{12 (M−1)} (f _i ) (18)
β (A _{12... (M−1)} (f _i ), A _M , R _M , f _i , φ ₀ ) = A _M · sin (α (Φ _{12... (M−1)} (f _i ), R _{M , f i, φ 0))} / [A 12 ... (M-1) (f i) + A M · cos (α (Φ 12 ... (M-1) (f i), R M, f i, φ 0 ))] ... (19)
It is.

By applying an induction method for the number of targets M to Equations 16 to 19, the beat signal amplitudes A _{12... M} (f _i ) and phases Φ _{12... M} (f _i ) are converted into amplitude parameters A ₁ , A _2. ... A _M , phase parameter φ ₀ , and position parameters R ₁ , R ₂ ... R _M can generate equations.

Here, the beat signal amplitude _{A 12 ...} M _{(f i)} and phase Φ _{12 ...} M _{(f i)} are known variables obtained by measuring the amplitude parameter _{A 1, A} 2 ... _{A M} and the phase parameter φ ₀ and the position parameters R ₁ , R ₂ ... _RM are unknown variables.

The frequency _{f i} N number of values (i = 1,2, ..., N ) when taken in, the beat signal amplitude _{A 12 ...} M a _{(f i)} and phase _{Φ 12 ... M (f i)} , the amplitude parameter and _{a 1,} a 2 ... a _M and the phase parameter phi _0, equations expressed in positional parameters _{R 1, R} 2 ... _{R M} is the 2N generated in total.

On the other hand, the total number of unknown variables [amplitude parameters A ₁ , A ₂ ... A _M , phase parameter φ ₀ and position parameters R ₁ , R ₂ ... R _M ] is 2M + 1. Incidentally, p pieces of positional parameters of the M position parameters _{R 1, R 2 ... R M} ( i.e., the vehicle _B 1 ... position of _{B p),} so obtained from the target-side speed detecting apparatus _4A 1 ... 4A _p Becomes a known parameter. Therefore, the number of net unknown parameters is (2M−p + 1).

Taking the number N of the frequency of the transmission signal that is a measurement frequency from this that the (2M-p + 1) / 2 or more, the target distance R _1, R 2 _... R _M is obtained by solving the above 2N number of simultaneous equations. Note that (2M−p + 1) / 2 is also q + (p + 1) / 2.

Incidentally, the above description be arbitrarily interchanged positional relationship between the vehicle B 1 _... vehicle B _p and the vehicle C 1 _... vehicle C _q holds it. In FIG. 6, the direction in which the target information detection device 3C irradiates the transmission wave Wt is the forward direction of the vehicle A. However, the irradiation direction of the transmission wave Wt is not particularly limited. As described above, the horizontal direction may be used.

In the present embodiment, using only the target information detection device that operates in the two-frequency CW method (multi-frequency CW method), the communication unit and the speed detection unit are used together, so that the two-frequency CW method or the multi-frequency CW method can be used. Even when the relative speed between the target information detection device and the target is “0”, the target information of each target can be acquired. Further, even when there are a plurality of targets having the same speed as the target information detection device, each target information can be acquired while identifying each target.

Therefore, the bandwidth of the RF signal and the BB signal can be made narrower than when a broadband radar system is used. This facilitates circuit design and enables cost reduction of the device. In addition, there is an effect that it is possible to avoid the problem of spectrum efficiency reduction and interference due to the broadening of the transmission signal G3.

Further, even when the relative speed between the target information detection device and the target can be regarded as “0” or approximately “0”, the target information can be acquired, so that the vehicle speed (throttle / throttle) is set so that the relative speed does not become “0”. Control such as automatic control of the brake is not required. Therefore, it is possible to detect the other vehicle while maintaining the state where the vehicle has moved at the same speed as that of the other vehicle, thereby obtaining an effect that enables stable movement.

Although the present invention has been described with reference to the embodiments (and examples), the present invention is not limited to the above embodiments (and examples). Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

This application claims priority based on Japanese Patent Application No. 2015-204174 filed on October 16, 2015, the entire disclosure of which is incorporated herein.

2 target information detection system 3 measurement side unit 3A measurement side speed detection device 3B measurement side communication device 3C target information detection device 4 target side unit 4A target side speed detection device 4B target side communication device 11 antenna 12 circulator 13 mixer unit 13a mixer 13b Band pass filter (BPF)
13c Analog-digital (A / D) converter 15 Oscillator 17 Fourier transform unit 18 ₁ ... 18 _N Fourier transformer 19 Calculator 20 Controller

Claims (6)

1. A target information detection system that irradiates a plurality of targets with a transmission wave having a predetermined frequency from a measurement-side moving body and obtains the distance between the measurement-side moving body and the target as target information from a Doppler frequency included in the reflected wave. ,
   A target information detection device for calculating the target information based on the Doppler frequency;
   A measurement side speed detection device for detecting the speed of the measurement side mobile body as a mobile body speed;
   A measurement-side communication device that at least includes a measurement-side communication device that communicates with the target information detection device and the measurement-side speed detection device; and a measurement-side unit mounted on the measurement-side moving body;
   A target-side speed detection device that detects the target speed as a target speed;
   A target-side unit mounted on the target, including at least a target-side communication device that communicates with the target-side speed detection device and the measurement-side communication device,
   When the target information detection device determines from the Doppler frequency that the relative speed between the measurement-side moving body and the target is equal to or lower than a preset mode switching speed, the target information detection mode is communicated from the Doppler mode. Switch to mode, acquire the moving body speed via the measurement side communication device, acquire the target speed via the measurement side communication device and the target side speed detection device, and Calculating the target information using the target speed;
   A target information detection system.
2. The target information detection system according to claim 1,
   The target information detection system is characterized in that the target information is measured by a multi-frequency CW method in which the number N of frequencies to be used is 2 or more (N ≧ 2: N is a positive integer).
3. The target information detection system according to claim 2,
   The target includes p first type targets (p is a positive integer) including the target-side communication device and the target-side speed detection device, and the target-side communication device and the target-side speed detection device include When the number of non-equipped second type targets is included (q is a positive integer), the number N of frequencies used by the target information detection device satisfies N ≧ q + (p + 1) / 2. Information detection system.
4. A target information detection method for irradiating a plurality of targets with a transmission wave having a predetermined frequency from a measurement-side moving body, and obtaining a distance between the measurement-side moving body and the target as target information from a Doppler frequency included in the reflected wave. ,
   The target information is calculated based on the Doppler frequency by a target information detection device,
   Calculate the speed of the measurement-side moving body as the moving body speed by the measurement-side speed detection device,
   Communicate with the target information detection device and the measurement side speed detection device by the measurement side communication device,
   The target speed is detected as a target speed by the target side speed detection device,
   Communicate with the target side speed detection device and the measurement side communication device by the target side communication device,
   When the relative speed between the measurement side moving body and the target is less than or equal to a preset mode switching speed from the Doppler frequency, the target information detection mode is switched from the Doppler mode to the communication mode, and the measurement side communication apparatus The mobile body speed is acquired via the measurement side communication device and the target side speed detection device, the target speed is acquired, and the target information is obtained using the mobile body speed and the target speed. calculate,
   A method for detecting target information.
5. The target information detection method according to claim 4,
   The target information detection apparatus measures the target information by a multi-frequency CW method in which the number N of frequencies to be used is 2 or more (N ≧ 2: N is a positive integer).
6. The target information detection method according to claim 5,
   The target includes p first-type targets (p is a positive integer) including the target side communication device and the target side speed detection device, and the target side communication device and the target side speed detection device. The number N of frequencies used by the target information detection apparatus satisfies N ≧ q + (p + 1) / 2 when q includes the second type target (q is a positive integer) that is not included. Target information detection method.

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